Analysis of a Nondegenerate Two-Photon Giant-Pulse Laser

In a recent article1to which we shall refer as [S&B], a two-photon laser was proposed and analyzed. This device consists of a cavity resonant at frequency vAand containing ions of type B with an inverted population NB/V between levels separated by an energy difference hvBsuch that vB= 2vA; it is necessary that the system not lase at vB, which criterion can be satisfied by low reflectivity of the cavity at frequency vB, by strong parasitic absorption in the laser material near frequency vB, or preferably by a choice of ion such that the transition vBis highly forbidden to a single-quantum process. The authors of [S&B] thus show that a certain priming density of photons of frequency vAwill provoke the simultaneous emission from the inverted population NBof pairs of photons vAat a rate exceeding the cavity loss,t he process diverging until the population inversion is eliminated.